The diacylglycerol kinase inhibitor, R59949, potentiates secretion but not increased phosphorylation of a 47 kDalton protein in human platelets.

We have investigated the action of a novel inhibitor of DG-kinase, R59949. This agent was found to produce partial inhibition of formation of phosphatidic acid in human platelets challenged with thrombin, DC8 or OAG. However, this effect was not associated with enhanced phosphorylation of a 47 kDa protein, a known substrate for protein kinase C. We therefore believe that this compound does not represent a major advance on its earlier prototype, R59022.